小电流接地系统接地故障电弧重燃暂态特征分析

Analysis on Arc Re-ignition Transient Characteristics for Grounding Fault in Non-solidly Grounding System

小电流接地系统单相接地故障时常具有间歇性,针对电弧重燃时刻与重燃时电气量的分析可完善故障暂态理论并提高检测效果。文中根据接地故障熄弧后的电压与绝缘恢复特点,分析不同接地系统中在故障点不同稳定情况时的可能重燃时刻,并对重燃后故障暂态特征进行分析。故障点稳定时,不接地系统中易在熄弧后半个工频周期内重燃;经消弧线圈接地系统中,重燃主要发生在故障相电压峰值前时刻。故障点不稳定时,重燃时刻无明显规律。将重燃过程看作非零初始状态的单相接地故障,高频暂态电流的谐振频率、衰减因子与重燃时刻无关,幅值与重燃时刻故障相电压瞬时值近似成正比,经消弧线圈接地系统中的衰减直流分量衰减因子与重燃时刻无关、幅值与相电压对时间导数近似成正比。仿真及实测数据验证了分析结论的正确性。

Single-phase grounding faults in non-solidly grounding systems are often accompanied by intermittent features. Analysis of the time of arc re-ignition and the electrical quantity when arc re-ignition happens can improve the fault transient theory and the effect of fault detection. Based on the recovery characteristics of voltage and insulation after arc extinction, the possible arc reignition time and the transient characteristics of the fault after arc re-ignition are analyzed under different stable conditions of the fault point in different grounding systems. When the fault point is stable, it is easy to re-ignite in the ungrounded system within half a power frequency period after the arc is extinguished. In the arc suppression coil grounding system, the arc re-ignition occurs mainly before the peak voltage of the fault phase. When the fault point is unstable, the re-ignition time is not obviously regular.Regarding the arc re-ignition process as a single-phase grounding fault in a non-zero initial state, the resonance frequency and damping factor of the high-frequency transient current are independent of the re-ignition time, and the amplitude is approximately proportional to the instantaneous value of the fault phase voltage at the re-ignition time. The damping factor of the attenuating DC component in resonant grounding system is independent of the re-ignition time, and its amplitude is approximately proportional to the derivative of phase voltage with time. The simulation and field data verify the correctness of the analysis conclusion.